1. Field of the Invention
The present invention is directed to the coloration of petroleum fuels. There is a need for dyes which are quickly and highly soluble in petroleum fuels such as, for example, gasoline, diesel oils and heating and fuels oils. As is pointed out in U.S. Pat. No. 3,764,273, this need arises because of the laws of certain foreign countries which impose taxes on motive and heating oils. These laws provide that particular dyes and/or marking agents must be added to these oils to provide a means for identification to prove or disprove the payment of taxes. For example, Manitoba Regulation 51/66 under the Motive Fuel Tax Act of Canada, provides in part that "Motive fuel used for any of the purposes mentioned in subsection (7) of Section 3 of the Act shall be given a specific colour and separate identity by means of a purple dye and a chemical marker, as may be determined by the minister."
A law passed in the Federal Republic of West Germany requires the addition of certain chemicals to distillate type heating oils sold in that country after Apr. 1, 1976. These chemicals are intended to permit the identification of taxed heating oils if used illegally for much more highly taxed diesel fuels. The opportunity for fraud exists because the chemical and physical properties of heating oils and of diesel oils are quite similar.
2. Description of the Prior Art
A great variety of azo dyes have been used for many years to color gasoline and other petroleum fuels and/or distillates. These dyes have usually been solid dyes in the form of powders, flakes, granules and the like which tend to cake and which have a limited solubility and a low rate of dissolution. For instance, the solubility of the various azo dyes used in the past has been of the order of magnitude of less than about 2%, ranging upward to about 5% in some instances. Further, and most importantly, the rate of dissolution of these solid dyes in gasolines, diesel and heating oils is very slow and requires special techniques. One such special technique is the so-called "dry dye eductor" system described in U.S. Pat. No. 2,925,333. In this same patent (at Column 6) it is disclosed that the solubility test was conducted by mixing gasoline with dye "on a slowly rotating wheel for 16 hours at 80.degree. F."
In addition, the use of powdered dyes causes (1) the evolution of noxious dye dust which exposes personnel to inhalation hazards requiring the adoption of precautionary measures and respiratory devices and (2) the deposition of dye dust on equipment and throughout the plant area requiring frequent cleanup.
Several solutions to these various problems have been suggested by the prior art. Thus, U.S. Pat. No. 3,049.533 attempts to overcome the caking and dusting problems by providing azo dyes in the form of thin platelets formed on a rotating drum.
Another solution to the problems associated with solid dyes is that of British Pat. No. 1,108,981 which solubilizes difficulty soluble solid dyes in a mixture of a liquid phenol and a hydrocarbon to provide a liquid dye. U.S. Pat. No. 3,690,809 also provides a liquid azo dyestuff by a particular combination of a mixture of azo dyes containing defined alkyl phenols or alkyl naphthols in the dye molecule together with a liquid organic viscosity depressant. Some well-known so-called "oil soluble" solid azo dyes used for coloring petroleum fuels include the following (where "C.I." refers to color index):
______________________________________ ##STR2## SOLVENT YELLOW NO. 56 C.I. 11021 ##STR3## SOLVENT YELLOW NO. 14 C.I. 12055 ##STR4## SOLVENT RED NO. 24 C.I. 26105 ##STR5## SOLVENT RED NO. 19 C.I. 26050 ______________________________________
Each of the foregoing dyes presents the same disadvantages previously noted for solid dyes in general. The solubility deficiencies of Solvent Red No. 19 (C.I. 26050) will be demonstrated more fully in the Examples hereinafter set forth.
As is readily apparent, an azo dye which has excellent solubility in petroleum fuels and exhibits good storage would be desirable to remedy the defects of solid azo dyes.
Accordingly, it is an object of this invention to provide azo dyes which have high solubility in petroleum fuels and a practically instantaneous rate of dissolution therein.
It is another object of this invention to provide azo dyes which have a high rate of solubility in petroleum fuels, a practically instantaneous rate of dissolution therein, exhibit storage stability and do not adversely affect the physical and chemical characteristics of the petroleum distillate to which the are added.